OBJECTIVES: 1. To determine the interrelationships of various erythropoietic progenitors employing in vitro colony forming techniques. The application of these techniques would be directed toward measuring the size and characteristics of these compartments in normal man and selected disease states associated with anemia or polycythemia. In addition, the types of hemoglobins synthesized by the various compartments would be analyzed using biosynthetic methods. 2. Development of a clinically useful assay for erythropoietin. This will employ a suspension culture system of canine marrow cells and 14-c-glycine as label. The purpose will be to establish a more sensitive assay to permit the ready distinction between various causes of polycythemia in man as well as kinetics of hormone turnover.